Discharges of hazardous organic compounds into the environment have led to contamination of surface water, soil, and aquifers resulting in potential public health problems and degradation of the land for future use. As used in this specification and appended claims, hazardous organic compound means a chemical or substance that is either toxic or highly toxic, an irritant, corrosive, a strong oxidizer, a strong reducer, a strong sensitizer, combustible, either flammable or extremely flammable, dangerously reactive, pyrophoric, pressure-generating, a compressed gas, a carcinogen, a teratogen, a mutagen, a reproductive toxic agent, or is suspected of having adverse health effects on humans. In many cases, subsurface groundwater contaminant plumes may extend hundreds to thousands of feet from the source area of a chemical release resulting in extensive contamination. These chemical contaminants may then be transported into drinking water sources, lakes, rivers, and even basements of homes.
The U.S. Environmental Protection Agency (USEPA) has established maximum concentration limits (MCL's) for various hazardous organic and inorganic compounds in water and soils. For instance, stringent drinking water limits placed on many solvent organic compounds in water can be as low as 0.005 mg/L (parts per billion).
The presence of hazardous compounds in subsurface soils, surface water, and groundwater is a well-documented and extensive problem. The source of these hazardous materials is often times from industry where the materials are released onto the soil surface or surface water or even into the subsurface soil and/or groundwater through leaking storage tanks. Many, if not most, of these compounds are capable of moving through the soil under the influence of moving water, gravity, or capillary action and serve as a source of groundwater contamination. As used in this specification and appended claims, soil is to be interpreted broadly to include all naturally occurring material found below ground surface (e.g. silts, clays, sands, rock, karsts, organics, tills, etc.).
Soil, surface water, groundwater, and wastewater can become contaminated by a variety of substances. The substances include, without limitation, metals, volatile, semi-volatile, and non-volatile organic compounds. Common examples of such contaminates include arsenic, barium, cadmium, chromium, lead, mercury, selenium, silver, PCBs, gasoline, oils, wood preservative wastes, and other hazardous organic compounds. Such other hazardous organic compounds may include, but not limited to, dioxane (such as 1,4-dioxane), chlorinated solvents (such as trichloroethylene (TCE), vinyl chloride, tetrachloroethylene (PCE), and dichloroethanes), ethylene dibromide, halobenzenes, polychlorinated biphenyls, acetone, ter-butyl alcohol, tert-butyl formate, and anilines. Additional contaminants include compounds containing at least one oxidizable aliphatic or aromatic compound and/or functional group (e.g. atrazine, benzene, butyl mercaptan, chlorobenzene, chloroethylvinyl ether, chloromethyl methyl ether, chlorophenol, chrysene, cyanide ion or organic cyanides, dichlorophenol, dichlorobenzene, dichloroethane, dichloroethene, dichloropropane, dichloropropene, ethyl alcohol, ethylbenzene, ethylene glycol, ethyl mercaptan, hydrogen sulfide, isopropyl alcohol, Lindane™, methylene chloride, methyl tert-butyl ether, naphthalene, nitrobenzene, nitrophenol, pentachlorophenol, phenanthrene, phenol, propylene, propylene glycol, Silvex™, Simazine™, sodium sulfide, tetrachloroethane, tetrachloroethene, toluene, trichlorobenzene, trichloroethane, trichloroethene, trichlorophenol, vinyl chloride, xylene, etc).
Contaminated groundwater and/or soil often must be removed or treated to make it less toxic and to meet federal and state regulatory requirements. There are a variety of reactants, biological remediation enhancing materials, and methods for treating contaminated soil, surface water, groundwater, and wastewater as discussed below.
Peroxydisulfate's have been reported as applied constituents for organic carbon digestion or decomposition. Application methods include thermally activated persulfate oxidation in conjunction with an electro-osmosis system to heat and transport persulfate anions into soils. Permanganate(s) and peroxygen(s) reactant(s) have also been reported as applied constituents for oxidation of organic compounds. Peroxygen compound(s) applied independently or in conjunction with a metallic salt catalyst(s) (complexed and not complexed; chelated and not chelated) have been shown to break down organic compounds within the soil, groundwater, and wastewater. Sorbent materials, such as activated carbon, have been used in situ to trap contaminants present in the soil and groundwater and to prevent further migration of contaminant plumes. Additionally, biological remediation can be supported and/or enhanced by in situ application of materials such as zero valent iron (ZVI), oxides, nitrates, oxygen releasing compounds, and organic substrates such as molasses, high fructose corn syrup, hydrogen releasing compounds, vegetable oils and emulsions, sodium lactate, lactic acid, sodium benzoate, proprionate, butyrate, chitin, mulch and compost, whey, and humic acids.
Groundwater and subsurface soil have been treated by injecting biological remediation enhancing materials, sorbent materials, or reactant(s) (with or without a catalyst(s)), within an aqueous mixture, slurry, or suspension into the subsurface. Another method for in situ treatment of groundwater includes the excavation of a trench proximate or downstream of a plume of contaminant(s). The trench is filled with biological remediation enhancing materials, sorbent materials, or reactant(s) and a permeable media(s) (i.e. sand) for the plume to flow through and the reactant(s) react with contaminant(s). These trenches filled with biological remediation enhancing materials, sorbent materials, or reactants are often referred to as permeable reactive barriers (PRBs). Limiting factors or disadvantages of these methods may include a) recovery of spent reactants, sorbent materials, or biological remediation enhancing materials, b) recharging the treatment system with biological remediation enhancing materials, sorbent materials, or unreacted reactant, c) obstructions such structures, roads, subsurface utilities, or other improvements to the land above or proximate the area of contamination.
Because of these limitations or disadvantages of the art before, there is a need for improved systems and methods of insitu treatment of groundwater and/or soil.